6 Answers
6

This is the traditional rule (iirc, Fowler’s discusses this at length). However, in colloquial usage, either option is fine, and are seems to now be somewhat more common, at least on teh internets. A commenter here nicely describes the sort of thought process which probably pushes people (usually subconsciously) towards using are:

I wanted to say that “neither of us are cardplayers”, but I know that in that case, I should use “is”. But I also can’t say “neither of us is cardplayers”. So perhaps I should say “neither of us is a cardplayer” which sounds ridiculous to me. Is the conclusion that, in situations like this, one should reconstruct the sentence entirely. So I should really say something like “we aren’t cardplayers”. Fine when you’re writing, but how do you avoid getting into a tangle when talking!!

FWIW, “neither of us is a cardplayer” and “neither of us are cardplayers” both sound absolutely fine to my ear.

I don’t have time at the moment, but if someone else is in the mood for some corpus or n-gram searching (or can find someone who’s already done the research), it would be very interesting to know the history of this. Is the current shift to neither … are a real phenomenon, or is this just recency illusion?

I think Fowler's simply wrong here. Ngrams shows they were equally common before 1800, and while "is" predominates nowadays, "are" is not at all uncommon.
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Peter Shor Apr 12 '12 at 10:48

@Peter Does it really show equal prevalence before 1800? Google's ngrams appear to jump all over the place before 1800, regardless of what you search for. So much noise--try altering the smoothing value. I wonder whether anything should even be hypothesized without error bars. Or does it simply mean that there were huge swings in vocabulary usage before big media, in our agrarian past? ;)
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MerkOct 19 '12 at 6:50

@Mark: They're fairly close to equal. The huge swings are because of the small sample size, which I should have compensated for by setting the smoothing value higher.
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Peter Shor Oct 21 '12 at 17:13

2

"Thersites' body is as good as Ajax',/ When neither are alive." — William Shakespeare, Cymbeline: IV, ii. So much for traditional rules and formal usage.
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RegDwigнt♦Oct 24 '12 at 11:19

I thought I'd add something to what has already been said in @PLL's answer. Merriam Webster's Dictionary of English Usage, which I like for its descriptive style and useful examples, has this to say about neither:

The reason it is sometimes plural is easy to see when you think about it. Neither serves as the negative counterpart of either, which is usually singular. But it also serves in the same way for both, which is usually plural.

The reason it seems more natural to use the plural verb to negate two choices is that we want to negate both choices, and not just one of them. For example, it may seem more natural to say, "Neither of these colours suit me" and "Neither yellow nor orange suits me".

It also says:

The singular number of neither is most likely to be ignored when it is followed by of and a plural noun or pronoun, for then both notional agreement and the principle of proximity pull in the direction of a plural verb.

It gives numerous examples of neither taking a plural verb:

Thersite's body is as good as Ajax'/When neither are alive--Shakespeare, Cymbeline, 1610

He had two job offers, but neither were ones he felt he could accept--Diana Diamond, N.Y. Times, 1974

In conclusion, it says this:

The pronoun neither, then, is not invariably singular, though it is more often so. When formal agreement obtains, it takes a singular verb. When notional agreement obtains, it takes either a singular or plural verb. These constructions are neither nonstandard or [sic] erroneous. If you are writing something in a highly formal style, you will probably want to use formal agreement throughout. Otherwise, follow your own inclination in choosing singular or plural constructions after neither.

Disjunction in the subject formally takes a verb that agrees in the number with whichever element is closest to the verb. This is just as true with neither/nor as it is with either/or. “Neither the Russians nor the Americans were ready to talk” is perfectly correct, but so is “Neither a British flag nor an American one flies above the pole.” The controversial case is disparate numbers where you actually have to check which part falls next to the verb, as in “Neither all the troops nor one general is ready” versus “Neither one general nor all the troops are ready”.
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tchristJul 15 '12 at 15:54

Despite what Fowler said, partitive constructions with neither seem to have taken mostly plural agreement until some time in the 1800s, as can be seen with the graphs for neither of them and neither of us. But it does seems that singular agreement is most common today.

Neither of them is/are

Neither of us is/are

You can really judge the usage much better by twiddling with the Ngram knobs. See, for instance here and here. Until the early 1800s, plural and singular were used roughly equally often.
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Peter Shor Jul 15 '12 at 13:44

Your wording is rather confusing and the formatting isn't exactly helping. Which option do you recommend now, and why? Is your intent to contradict the answers already posted, or supplement them? It's not clear to me at all.
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RegDwigнt♦Apr 12 '12 at 10:28

That's not right. Your reasoning is flawed. For example you can say 0 of them is awesome. This is essentially the same as neither.
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Matt E. Эллен♦Apr 12 '12 at 11:34

0 of them are awesome. Just like you would say none of them are awesome. Another example: None [of these sweaters] are blue.
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RoyApr 12 '12 at 13:05

Hi RegDwight: To clarify: Neither refers to 2 or more. You can't use neither to refer to one option directly and also it can't be used for no choice arguments (or zero options).
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RoyApr 12 '12 at 13:07

hm, that makes sense, but I think neither is still singular because it's referring to each of them, not the group. "both" would be plural and refer to font color and text as a group.
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adamboxFeb 1 '11 at 23:02